RNA binding proteins are necessary for the growth and development of various cells. These proteins are involved in the splicing, editing, transporting and localizing of RNA, and mRNA post-transcription control. These proteins have special RNA binding domains so as to bind with RNA. Many conserved RNA binding motifs have been found by amino acid homology and structural similarity analysis on these RNA binding domains. These motifs include RNP motif, arginine rich motif, zinc finger motif, Y box, KH motif and double-stranded RNA binding motif, etc., and each of them has a special conservative sequence (Burd,C. G. and Dreyfuss,G. (1994) Science,265:615-621).
An RNP motif consists of about 90 amino acids, and h as two highly conservative regions. One is a hydrophilic fragment with 6 amino acid residues PNP-2 motif, the other is a motif with 8 amino acid residues RNP-1 or RNP-CS motif). The RNP domain exists in at least 25 kinds of proteins, including nonhomogeneous ribonucleoprotein (hnRNPA, hnRNPC, hnRNPE, hnRNPG, etc.), small molecular ribonucleoprotein (U1 SNRNPA, U2 snRNPB, etc.), pre-RNA and mRNA-related protein (for example, protein synthesis initiation factor 4B, nucleolin, polyA binding protein, etc.) and many other proteins (for example, drosophila sex-determing protein, Sx1 protein and Tra-2 protein, La antigen, 60 kd Ro protein, murine insulin induced responsive protein Cl-4, etc.